Improving plastic recycling with hyperspectral imaging

Plastic waste has become one of Australia’s greatest environmental concerns. Recycling discarded materials is a critical challenge, and one in which the implementation of hyperspectral imaging technology offers benefits.

Unfortunately, our use of plastic products is one of ‘make, take, and throw’, without thinking of its long-lasting impact on the environment. A recent CSIRO report, Advanced recycling technologies to address Australia’s plastic waste, showed human consumption of plastic over the period of 2016-17 reached some 3.4m tonnes. However, the following year, Australia managed to recycle less than 10% of all this waste! Reducing plastic waste is critical to our environment and our economy. Australia can no longer export waste to China, so we must find ways to deal effectively with it ourselves. Today, only half of our end-of-life plastics are recycled – some is compressed to go into landfill, taking decades to breakdown while exuding dangerous gases; some is incinerated; polluting the air; while other waste finds its way into the ocean with devastating consequences on bird and marine life. However, there is a way to rectify this by building a circular economy through effective plastic recycling processes. Due to plastic’s flexible usage, not all discarded plastic is the same, with differing chemical structures used to make different products. Plastic drink bottles are made from polyethylene terephthalate (PET); pipes made from polyvinyl chloride (PVC) are installed in plumbing applications around our homes; while low-density polyethylene (LDPE) is used in consumable products such as plastic bags, food packaging and coffee cups. Discarded plastics received at garbage centres are generally transported as mixed loads to mechanical recycling plants, where sorting process removes other waste. However, this process can be greatly improved with the implementation of hyperspectral imaging technology. Hyperspectral imaging cameras are used across Europe to improve identification of plastics in mixed garbage. The camera can capture both the spatial and spectral images of each item, making separation easier. Due to their chemical structure, all plastic types have unique spectral properties that cannot be identified by an RGB camera or human eye. Commonly used plastics have unique spectral properties, but due to their similar chemical structures, the spectral differences are small, sp high spectral resolution is required. Using spatial resolution, a HySpex camera can separate even small plastic pieces passing along a conveyor belt at high speed. The spectral differences identified during data analysis provides the basis for a robust classification model that can be used with every mechanical sort. Originally developed for defence purposes by NEO in Norway, HySpex cameras are being applied in such diverse tasks as identifying ore patterns in mining sites, or finding nematodes in fish fillets. Governments are recognising the need for innovative technology in this area, with recently released grant funding encouraging recyclers to find new ways to capture the value of our plastic waste and build a circular economy through effective recycling. A circular economy is one where plastic waste must be recycled into new products. The Australian Packaging Covenant has set targets for a true circular economy to be reached by 2025. To reach a true circular economy requires adopting technical innovation to improve current practices of mechanical recycling, and even to adopt advanced recycling techniques. Both of these recycling processes have a part to play. The most common form of recycling in Australia is mechanical recycling, where plastic is separated from other garbage, then chopped, washed, and melted into granulates for extrusion into new plastic products. But more than that can be achieved where gains are measured in real economic value. An amazing example of innovation can be found in NSW, where one company is taking broken down plastic waste and using an environmentally friendly process to convert it into bio-crude oil. Advanced recycling such as that being used by the processing plant in NSW, recovers the chemical building blocks that make up the plastic product. When we think of plastic waste, we usually think of plastic bottles. But polymers are used in many other things, such as clothing, carpets, packaging, toys or car seats. These are all amenable to recycling. This is where advanced or chemical recycling works in partnership with mechanical recycling, as it can handle problematic items that have for many years gone into landfill, leaving plastics to contaminate the environment for decades. Introducing innovation to improve current garbage sorting systems is the first step to better processing. Indeed, mechanical recycling is more effective when the waste is sorted into plastic that is suitable for mechanical processing, and those that require separation for advanced processing. In Europe, according to a 2020 study, mechanical recycling was used to process more than 5m tonnes of waste. Now HySpex hyperspectral imaging cameras are offering innovation to the process of separating plastic types, providing the building blocks of a circular economy. Sorting plastic waste is problematic, not just for households, but for waste recycling companies dealing with mixed plastic waste. Hyperspectral cameras offer an innovative solution for recycling companies in sorting plastic waste that might be used more effectively to the benefit of both our environmental health and the economy. HySpex hyperspectral imaging cameras support plastic recycling processes with high-quality, customised, industrial-scale turnkey solutions. www.raymax.com.au